THE SHELF — a risk curve you can read before you dive
A chain of pressure domes on a continental shelf, and a trench below them. The engine is unchanged. The theme pack renames the nouns and adds the mechanic the theme was built for: depth is the tier ladder, and the failure chance for every depth is printed in the rules.
01The pitch
You live in a dome and work downward. Every metre below the shelf is more yield and more chance of not coming back, and both numbers are published before you queue the dive. There is no hidden difficulty: the game tells you the odds, and the log keeps the result.
The fantasy is the descent — a seal crew holding a dome, a diver on a trench line, a grower keeping the kelp rows. The late game is an office: Diver Marshal, who licenses who may dive depth 4 and below; Seal Warden; Pump Master. The endgame is a dome you own, at the depth you can defend.
Why this theme is third: the published risk curve is the honest answer to the genre's secret numbers, and here that honesty is the whole game. A player who can compute a dive is a player who trusts the engine.
02The theme pack — the engine's nouns, in theme words
Four bars, four stats, six jobs, twelve acts, six offices, twelve commodities. The numbers are the prototype's starting values, sized so a season in any theme is comparable to a season in another. This is the theme file, printed.
The bars (renamed, same shape)
| Engine bar | Theme name | Spent on | Recovery rule the theme supplies |
|---|---|---|---|
| Vigour | Lungs | diving, pumping, the dome shift, the grow rows | a pressure cycle: a facility sets the recovery, and the dome sets the cap |
| Nerve | Pressure | the trench, the deep dock, salvage below the shelf | rest, and a decompression rota the Pump Master sets |
| Focus | Seal | sealing, glass, repair, survey, teaching | a seal shop: a facility raises the Seal cap |
| Standing | Dome | contracts, office, teaching, command of a dome | the dome roll: an office restores a standing, a court lowers it |
The jobs (6)
| Job | Wage / day | Stat gain | Requires | Daily points, spent on promotions |
|---|---|---|---|---|
| Dome hand | 200 | Body +1 | none | Dome points |
| Grower | 240 | Body +1, Seal +1 | a row share | Kelp points |
| Seal crew | 300 | Seal +2 | Seal ≥ 15 | Seal points |
| Pump crew | 340 | Body +2 | Lungs ≥ 40 | Pump points |
| Trench runner | 440 | Pressure +2, Body +1 | Dome ≥ 25 | Trench points |
| Diver | 500 | Lungs +2, Pressure +1 | Dome ≥ 35, a dive licence | Dive points |
The acts (12) — a theme names the verbs, and only names them
| Theme name | Engine act | Cost | Ticks | Published risk | Published reward |
|---|---|---|---|---|---|
| seal a joint | upkeep | Seal 8 | 2 | 6 % leak | dome integrity +3 |
| a dive to depth 2 | risk | Lungs 12, Pressure 6 | 2 | 5 % loss | 180–360 |
| a dive to depth 4 | risk | Lungs 18, Pressure 12 | 3 | 14 % loss | 420–880 |
| a trench run | risk | Lungs 24, Pressure 18 | 5 | 26 % loss | 700–1,500 |
| pump the shelf | office | Body 10 | 1 / tick | 0 % | water +, dome stable |
| grow the kelp rows | freight | Body 10, Seal 4 | 3 | 7 % blight | 120–300 |
| haul to the dock | freight | Lungs 10 | 2 | 3 % spoil | 100–240 |
| salvage below the shelf | risk | Pressure 20, Lungs 16 | 5 | 30 % loss | 600–1,600 |
| rescue a diver | teach | Pressure 14, Dome 6 | 2 | 10 % loss | a diver returned, Dome + |
| pressure check | defence | Seal 6, Dome 4 | 1 | 0 % | an integrity read, printed |
| teach an apprentice | teach | Seal 6, Dome 4 | 2 | 0 % | apprentice gain +1 |
| garrison a dome | defence | Lungs 8, Dome 5 | 1 / tick | 0 % | defence + garrison value |
The map — the prototype's six districts, tiered
| Tier | Position | Yield / day | Garrison required | Upkeep / day |
|---|---|---|---|---|
| 1 | the shelf dome | 20 | 2 | 5 |
| 2 | the reef dock | 60 | 6 | 14 |
| 3 | the mid dome | 110 | 10 | 25 |
| 4 | the deep dock | 180 | 12 | 35 |
| 5 | the trench station | 320 | 18 | 60 |
| 6 | the floor | 600 | 26 | 120 |
Offices, commodities, currency
03The signature mechanic: The Depth Ledger
One mechanic per theme, and one only — the rule that keeps five themes on one engine. The formula below is what the engine computes every tick, printed in the rules page in the game.
Why it is a mechanic, not a flavour
The odds are printed
A player computes expected value before queueing. That is the design answer to secret numbers: the game does not hide the risk curve, and a loss is a number the player accepted.
A licence is an office, not a level
The Diver Marshal decides who may dive depth 4. A judgement a player makes in public, audited in the log; the season's politics are licence politics.
The deepest tier is a position, not a level
The floor is a district with a garrison, not a difficulty setting. Owning it means defending it, and a strong guild cannot take it from someone who garrisons it.
Beat 1
the shelf dome is crewed (40 names)
Beat 2
the first depth audit: every dive's published risk, printed
Beat 3
the reef dock opens (tier 2)
Beat 4
a dive fails at depth 4 — the first loss, in the log
Beat 5
the Seal Warden sets the repair rota
Beat 6
the trench station is reached (tier 5)
Beat 7
a dive licence is refused, and appealed in the court
Beat 8
the Diver Marshal election
Beat 9
a dive-share contract, executed by the engine
Beat 10
the floor is contested (tier 6)
Beat 11
licence reform: depth is licensed by the guild, with an appeal
Beat 12
the season ledger publishes every dive, every depth, every result
04Art direction, and the feel
Text-first: no images, no animation, no sound. The theme supplies words, a palette, and a shape, and every object carries its numbers in text.
05What breaks this theme
The risks, named before anyone builds it. Each one has a test attached, so the honest list is a plan, not a mood.
A published risk curve makes gambling legible Undecided
Players will push the top tier and take the loss, which is exactly what the theme asks of them. The expected-value line is the balance knob: if a depth-6 dive has positive expected value, the top tier is a lottery, not a position.
Test: Print the expected-value table for the season's top three depths in week 4.
Drowning is a shared loss Undecided
A diver who dies is a dome's labour force, and the loss lands on a group. The same problem as the station: a collective cost for an individual act.
Test: Count grievances against shared pools in season 1.
Nobody plays a water game on a phone Undecided
The genre's market is crime and neon. The deep theme is the least marketable of the five, and the most legible of the honest ones.
Test: Ask the cohort which theme they would play, blind, from the pack table alone.
Depth is a ladder, and ladders end Undecided
Six tiers is a short map. A season that reaches the floor has nothing below it, so the theme needs a new shelf each season, which is content, not mechanics.
Test: Measure the share of districts changing hands in the last 4 weeks.
A licence is a gate a player holds Undecided
The Diver Marshal decides who is allowed to risk their life. It is a fair office, and it will be used unfairly at least once, in public, in the log.
Test: Count licence appeals in the season ledger.
It is the theme where the published numbers are the product. A player who can compute the odds trusts the engine, and a player who trusts the engine is the thing the genre's players have never been given.